1. Field of the Invention
The present invention relates generally to a mobile communication system supporting multimedia services including data and voice services, and in particular, to a method and apparatus for transmitting and receiving between a base station (BS) and a mobile station (MS) information about the available orthogonal codes to the MS.
2. Description of the Related Art
A typical mobile communication system, for example, a CDMA (Code Division Multiple Access) mobile communication system such as an IS-2000 system supports only voice service. Growing user demands and communication technology development have resulted in the development of a mobile communication system supporting data service. The HDR (High Data Rate) system was proposed to support high-speed data service only.
Thus, existing mobile communication systems support either of voice and data services. To satisfy a need for contemporaneous provision of voice and data, a so-called 1xEV-DV (Evolution-Data and Voice) mobile communication system has been proposed.
In view of supporting only data transmission, the number and type of orthogonal codes (e.g., Walsh codes) available to a BS are fixed in HDR. However, the number and type of Walsh codes available for data service are variable depending on the absence or presence of voice service users and the number of the voice service users in 1xEV-DV. Hence a BS tells an MS about the available Walsh codes to the MS.
HDR also differs from 1xEV-DV in that only one MS receives a data service at a certain time, while two or more MSs can receive the data service simultaneously in CDM (Code Division Multiplexing) for a predetermined time period. To do so, the BS transmits to the MSs information about Walsh codes available to them in a given Walsh code index.